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Amlodipine is a calcium channel blocker and anti-hypertensive compound, but had originally been formulated in the form of the maleate salt. However, when problems with stability and processability arose during the regulatory approval process, Pfizer began to search for a different salt through an accepted process known as salt screening. During this process, Pfizer tested seven other salts, and decided to proceed with the besylate salt. Pfizer then filed a patent application directed to the besylate salt of amlodipine based on its alleged unique combination of properties that made it particularly suitable for preparing formulations of amlodipine. This application subsequently issued as the ‘393 Patent.

In his decision, the trial judge discussed the development of pharmaceutical products in the 1980’s (particularly the salt screening stage), detailed both the development of amlodipine besylate and the patenting thereof, and thoroughly summarized all expert evidence in relation thereto. The trial judge concluded that the ‘393 patent was invalid for obviousness, as well as finding, in obiter, that it was invalid on a number of other grounds, including: lack of utility; insufficient disclosure; misleading under s. 53 of the Patent Act; and that it failed to meet the criteria for a valid selection patent. Pfizer appealed the decision on both factual and legal grounds.

Regarding the alleged factual error, Pfizer asserted that the trial judge erred in finding that a person skilled in the art “would have had every reason to test the besylate salt.” Specifically, Pfizer argued that the trial judge erred by focussing on the process the inventors used in developing the invention rather than the outcome or result of the process. Pfizer submitted that, when an invention is arrived at through testing, it is not necessarily obvious merely because the utilized tests were within the knowledge and capacity of the person skilled in the art. Instead, according to Pfizer, the invention is obvious only if its result was obvious. In this respect, Pfizer complained that its cross-examination of one of ratiopharm’s experts demonstrated that the result was not obvious. The Court of Appeal summarily dismissed Pfizer’s argument, characterizing it as “a complaint that the trial judge was insufficiently persuaded by Pfizer’s cross-examination”. This did not demonstrate palpable and overriding error.

Regarding the alleged legal error, Pfizer argued that the trial judge misapplied the “obvious to try test” in an obviousness inquiry. Specifically, Pfizer maintained that the trial judge asked whether the process was more or less self-evident (or predictable) when the appropriate question was whether the result was self-evident (or predictable). Accordingly, in Pfizer’s view, the trial judge misdirected himself as to the law. Furthermore, Pfizer argued that the trial judge erroneously relied upon and adopted similar reasoning from U.S. authority on the same issue. Again, the Court of Appeal rejected Pfizer’s position, stating that it was “a disguised attempt to challenge factual determinations by characterizing them as errors of law.” Statements made by the trial judge regarding the U.S. decision were in obiter, and the trial judge had explicitly recognized that somewhat different principles applied in Canada. Consequently, no legal or factual errors had been committed, and the appeal was dismissed with costs.